Immobilisation of a biological chelate in porous mesostructured silica for selective metal removal from wastewater and its recovery

Abstract

This study represents a preliminary stage in the development of a process aimed at the selective uptake and release of metal ions from wastewater. The process involves the immobilisation of highly selective natural chelates secreted by bacteria or other living species inside mesoporous micelle-templated silicas (MTS) that could be used as usual resins. To demonstrate the feasibility of the concept, a model system was used. It involves pyoverdin, a natural Fe(III) chelator from a Pseudomonas fluorescens strain, covalently anchored to a glycidoxypropyl linker into the large pores (13 nm) of a MTS material. The hybrid material obtained is very stable as no leaching of the pyoverdin complex was observed during repeated washings and repeated uses. The native fluorescence of the pyoverdin allows a simpler follow-up and quantification of the iron uptake and release processes. The pyoverdin-anchored MTS is very selective towards Fe(III) if a multi-metallic solution is used. MTS materials allow a higher density of pyoverdin anchoring and consequently a higher metal uptake, compared to a high-grade silica gel.